(i) Field of the Invention
This invention relates to an externally-mounted, stationary-design, self-aligning rotary face-seal for inhibiting any fluid or product flow through a space formed, for example, between a casing and a rotary shaft extending through the casing. More particularly, it relates to an externally-mounted, stationary-design, self-aligning rotary face-seal for inhibiting any fluid or product flow between two relatively rotating faces, e.g., the end faces of a rotary ring fitted to a rotary shaft and of a stationary ring fitted to the casing. In this invention, the face which is free to move axially, by means of forces applied by the resilient operator is the non-rotating face. In most mechanical face-seal designs, it is the rotary face which is directly acted upon by the force applied by the resilient operator.
(ii) Description of the Prior Art
Many shaft seals have been proposed which are basically constructed such that a rotary ring fitted onto a rotary shaft, in an axially-slidable manner is thrusted by means of a spring located behind the rotary ring until the end face of the latter comes into tight contact with the end face of a stationary ring fitted to a casing. In this way, fluid-tightness is ensured between the end faces of the rotating and stationary rings while sliding contact is maintained at the contact area therebetween. Since the spring is disposed so as to thrust the rotary ring in the axial direction, a large volume of axial space must be occupied by the spring.
U.S. Pat No. 4,413,831 patented Nov. 8, 1983 by A. Washida et al attempted to provide a solution to the problem of a large axial space required for the spring. That patentee provided a shaft seal device, which included a cylindrical seal ring member made of elastomeric material disposed between a rotary ring, which was fluid-tightly fitted onto the rotating member, and a stationary ring, which was fluid-tightly fitted onto the stationary member. Both the end faces thereof came in contact with the corresponding faces of the stationary member and the rotating member. The seal ring member had at least two annular grooves formed on its outer surface, and ring-shaped resilient means were fitted into each such annular groove, so that both the end faces of the seal ring member were forcibly thrusted against the corresponding faces of the rotary ring and the stationary ring under the influence of the contractive force of the resilient means, thereby to ensure fluid-tightness therebetween. A progressive seal ring made of a fluororesin was fixedly-secured to the end face of the stationary ring.
This patent suffered numerous shortcomings, including the complexity of assembling the seal device upon installation or subsequent servicing. It was not designed to be splittable to be easily retrofitted to existing equipment, nor was it designed to be mounted externally (i.e., on the atmospheric side of the equipment casing) to facilitate installation or replacement of wearable components. In fact, it required a precisely dimensioned internal counterbore into which the stationary ring was pressed and retained, as well as a predetermined and fixed axial distance between the internal face of the equipment and the rotating member, between which the stationary assembly portion is disposed. By virtue of these shortcomings, it is apparent that a specific piece of equipment must be either originally designed to accommodate this shaft seal device, or be later modified, if possible, to accept it. It is also apparent that this device cannot be either installed, serviced or replaced upon failure or wearing-out, without removing from service and dismantling the equipment and reassembling, usually at considerable expense and effort.
Other patents have provided clamping members in the form of a circumferential band clamp. For example, in U.S. Pat. No. 3,689,084 patented Sep. 5, 1972 by R. W. Smedly, an auxiliary oil seal was provided, for installation upon a gear box and associated shaft which had developed a fluid leak through a previously installed oil seal. A flexible seal member was installed around the rotatable shaft adjacent to the stationary gear box wall. The seal member was then secured to the stationary wall using a settable plastic or other similar means. A circumferential clamp could be secured around the outside of the seal member, simply to retain it in its installed position, with its cut-ends abutting each other.
This patent suffered numerous shortcomings. In this design, there was no means of manually-adjusting the sealing-contact, and, as is the case with virtually all radial lip-seal type devices, it was relatively limited in its self-compensating (for relative shaft movement and wear) capabilities.
U.S. Pat. No. 4,296,935 patented Oct. 27, 1981 by Hitachi Ltd. provided an internal mechanical seal for a rotary shaft which included the provision of axial force from bias springs, disposed loosely in a well in a retainer to urge an axially movable ring towards a seal ring and thus to provide seal faces. In This structure, it was difficult to maintain the springs in the well for the purpose of assembly.
This patent suffered many other disadvantages. It was not designed to be splitable to be easily retrofitted to existing equipment, nor was it designed to be mounted externally (i.e., on the atmospheric side of the equipment casing) to facilitate installation or replacement of wearable components. In fact, it requires a precisely dimensioned internal counterbore as well as a predetermined axial distance between the internal face of the equipment and the rotating member, between which the stationary assembly portion was disposed. By virtue of these shortcomings, it is apparent that a specific piece of equipment must be either originally designed to accommodate this mechanical shaft seal or be later modified, if possible, to accept it. It is also apparent that this device cannot be either installed, serviced or replaced upon failure or wearing-out, without removing from service and dismantling the equipment and reassembling, usually at considerable expense and effort.
U.S. Pat. No. 4,576,384 patented Mar. 18, 1986 to A. W. Chesterton Co. provided a split mechanical face seal in which the rings were non-rigidly supported in an axial direction by resilient support means axially biasing the sealing surfaces of the rings together.
This structure had several drawbacks, not the least among them being that it was relatively complex and consequently difficult and time-consuming to install, and would prove relatively demanding with regards to manufacturing processes and consequently be quite expensive. Also, it was very limited in regards to its capabilities to perform satisfactorily under adverse mechanical conditions, e.g. as often was encountered with rotating equipment subject to excessive relative shaft movements (angular, axial and radial).
U.S. Pat. No. 3,988,026 patented Oct. 26, 1976 by O. E. Kemp Jr. provided what was purported to be a self-compensating rotary seal member. As described, such seal was not split and therefore was not easy to retrofit to existing equipment. To install such seal on existing equipment, the equipment would have to be disassembled. Such seal could compensate for some degree of radial movement (eccentricities) and angular tilting, but not for axial displacements. It was only capable of performing on low-pressure applications. The pressure of the media being contained acted to force the seal faces open, rather than serving to urge the seal faces into rotatable sealing contact.
In spite of these prior patents there is still a need for a simple, effective and economical seal which can be easily retro-fitted to existing equipment, and which will function even under extremely adverse mechanical conditions, as is often encountered with older, worn equipment and the like.